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From Inspiration to Application

A meeting of minds

Dr. Gérard Mourou, professor at the École Polytechnique and Physics Nobel Laureate, Prof. Dr. Michael Kaschke, ZEISS President and CEO, and Prof. Dr. Andreas Tünnermann, Head of the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) and Director of the Institute of Applied Physics at the University of Jena, discuss the interdependence of basic science, applied research, and the research being conducted in the industry. The three of them met after the opening of the Max Planck School of Photonics in Jena, where they discussed high-power lasers and how they have redefined basic science, engineering, and medical treatments for patients.

As representatives of basic, applied, and industrial research, what do you feel you have in common?

Prof. Dr. Michael Kaschke:

At the heart of any scientific discovery or innovation lies an approach characterized by problem-solving, an openness for new challenges, and sheer curiosity. This approach is just one element of what we call “Seeing Beyond,” which is the mindset that we here at ZEISS believe is the right mindset for a leading company. It is a mindset to go curiously where others have not gone before, to look ahead and tackle problems that may only be emerging. I believe this fascinates all three of us here today – we simply represent this mindset in different ways.

Prof. Dr. Andreas Tünnermann:

I think that’s very true. The discovery of chirped pulse amplification (CPA) by Gérard Mourou and his colleagues exemplifies how breakthroughs in science that are based on this openness can lead to transformative applications, for example in laser eye surgery, which ZEISS pioneered.

Professor Mourou, looking back at the time you and your team made the breakthrough that later won you the Nobel Prize shows how fast paradigms can change. Wouldn’t you agree?

Prof. Dr. Gérard Mourou:

That’s true. It’s funny to think back to the reactions I received in 1988 when I talked about chirped pulse amplification (CPA) producing terawatts. People did not believe I was talking seriously. At the time, a high-power laser was measured in gigawatts (10⁹ W), and I was starting to talk about terawatts (1012 W). This was at the University of Rochester, where the terawatt lasers took up an entire building. CPA then brought us tabletop terawatt lasers.

Seeing Beyond is a mindset to go curiously where others have not gone before, to look ahead and tackle problems that may only be emerging.

How long did it take to come up with feasible applications?

Prof. Dr. Michael Kaschke:

The time it took to move from these breakthroughs to an application, for instance in ophthalmology, was actually quite short. Even back then, our typical timeframe from lab to market was 15 years, which is what we call the three-times-five-years rule. This entails five years for prototypes, five years for clinical trials, and five years for market acceptance. I think this is a fine example of the amount of work you have to put in before you’re really ready to exploit a discovery.

Prof. Dr. Gérard Mourou:

Don’t discount the role of luck! In our case working with the cornea, it all began by accident. You may not know this, but one of my students was working on the first high-power systems and the laser beam came into contact with his eye. We took him to the hospital where we were told that, fortunately, the retina had not been affected, but the “cut” on the cornea was perfect. This was in around ’93 – medical applications came to market about 10 years later. This took time because, as Michael said, first we had to conduct all the medical trials.

Prof. Dr. Michael Kaschke:

You’ve just made a very profound point, Gérard. The systematic process that enables us to search for discoveries is vital, but we must not forget the equally important and vital element of luck. That’s why we must learn from any mistakes and recognize that these are needed to ultimately make discoveries and create innovations.

Is the same true for applied research?

Prof. Dr. Andreas Tünnermann:

Looking at the learning element in innovation, I can easily now say that applied research comes along with trial and error aiming for learning and growing. Providing an environment where you can best learn from failure, is the mission of Fraunhofer IOF.

Prof. Dr. Michael Kaschke:

Indeed we need a culture of knowledge inquiry and sharing.

Fotografie: Dominik Gigler

Prof. Gérard Mourou was awarded the Nobel Prize in Physics in 2018. The French physicist has been working in laser physics and nonlinear optics for more than 40 years. In 1990, he founded the Center for Ultrafast Optical Science at the University of Michigan. Today he is Director of the Laboratoire d'Optique Appliquée in the southwest of Paris. Together with his doctoral student Donna Strickland, Gérard Mourou is considered one of the inventors of Chirped Pulse Amplification (CPA). This technique makes the generation of very short laser pulses reaching intensity levels in the petawatt range possible. The CPA is used in both industrial as well as medical applications.

Professor Mourou, can you tell us a bit more about the frontiers of today’s extreme laser physics, 30 years after CPA?

Prof. Dr. Gérard Mourou:

Well, it is still about achieving higher and higher power in laser development. Today we have petawatt lasers (1015 W), which offer greater performance than all the power stations in the world can produce, but just for a short time. In the future, we will probably see exawatt lasers and then we will have tabletop proton accelerators.

Prof. Dr. Michael Kaschke:

When do you think we will integrate such a laser-based protonaccelerator in real-world applications – in medical applications, say? Will it be another 10–15 years before we see any clinical applications?

Prof. Dr. Gérard Mourou:

Laser proton accelerators are already around today, and we can use them to produce protons. But the maximum proton energy is something like 1,000 MeV. For therapy you’ll need higher energies. One possible approach I am looking at are shorter pulses – perhaps not much shorter but a single cycle. So I’d say 10–15 years is a realistic time frame.

Looking at the end of this continuum, from basic science to industry, what exciting developments can we expect to see at ZEISS and in the optical and photonics industry in general?

Prof. Dr. Michael Kaschke:

There’s a lot of exciting stuff happening, first and foremost in biomedical and lithography technologies. We are talking a lot about protons because of how lasers, and especially high-power femtosecond lasers based on CPA, have made their way into very precise tissue manipulation. I call this the “art of precise surgery.” At some stage we will probably be using semi-robotic lasers that may allow surgeons to perform operations on an almost cellular level. This once again calls for shorter wavelengths because ultimately we have to think about how we can work inside the cell.

Right now the focus is on multi-cellular surgery, but the interesting thing is how to get really close to a disease, i.e. how can we “operate” inside a cell.

With regard to lithography, EUV allows us to go down to a one-two nanometer structure size. Ten, fifteen years from now, we will be getting closer to the atomic level. This is going to be very interesting, especially from a fundamental science perspective.

Prof. Dr. Andreas Tünnermann:

That’s absolutely fascinating from a scientific point of view, so to go from structures for electronic applications right through to the atomic level.

Prof. Dr. Michael Kaschke:

Absolutely! In my opinion this is still more than ten years away, so we will see a couple of iterations before then. An interesting question is whether this will revolutionize electronics as we know it.

Prof. Dr. Andreas Tünnermann:

A lot of people are talking about quantum technologies as the field of the future.

Prof. Dr. Michael Kaschke:

You cannot have quantum technology without optics and photonics. I see quantum sensing coming, as well as quantum microscopy. I’m somewhat less optimistic than many others about the timescale for the widespread use of quantum computing; I still see this as being several years away. But when it comes to quantum states used for sensing or even imaging, I believe we’re much closer to achieving those.

Fotografie: Dominik Gigler

Prof. Dr. Andreas Tünnermann heads the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena. The Doctor of Physics dedicated his final thesis at the University of Hanover to the topic "Interaction of Intense Laser radiation with Atomic Gases and Vapors: New Methods for the Realization of Short-Wave Coherent Radiation". Tünnermann's research focuses on fiber and waveguide lasers. He succeeded in significantly increasing the continuous output power of the lasers and optimizing their optical properties. He was also able to substantially improve the beam quality of ultrashort signals.

Professor Tünnermann, at the Fraunhofer IOF you are developing fibers for the next generation of high-performance lasers. What are the potential applications?

Prof. Dr. Andreas Tünnermann:

At the Fraunhofer IOF, we are currently developing a generation of optical fibers that will open up unique possibilities for controlling light. The focus is on active fibers, for example for the generation of ultra-short high-energy pulses in fibers. Another area we’re focusing on is on developing concepts for transport fibers that guide laser beams with very high powers across large distances. Similar to the revolution in laser material processing with a combination of glass fibers and solid-state lasers in the 1990s, in the future optical fibers will distribute the energy of ultrashort-pulse lasers and drive completely new applications. This requires light transmission where the pulse is not affected by interaction with the fiber. One example of this are hollow-core fibers that guide light in air and thus minimize unwanted effects during transmission.

Prof. Dr. Michael Kaschke:

This is a good example of how extreme physics is putting new demands on technology. It’s also another point where our worlds of science and industry converge, and is what I often call the Apollo effect: you go in one direction with your research but you encounter challenges in a different direction and you need engineers to clear the path, which then opens up new directions for research.

The example I always give is the manufacturing technology that we use for the extreme ultraviolet (EUV) mirrors, which was actually developed one or two decades ago for X-ray satellites in space. It was an astronomy project that wasn’t really a commercial success for ZEISS but, in terms of expertise and development, was very important. These “by-products” occur when you push the boundaries of physics. This is why what you’re doing, Gérard, is already really extreme physics because you’re basically probing totally new energy levels, and this will have an impact on applied research, and even engineering.

Prof. Dr. Andreas Tünnermann:

Yes, and let’s not forget that the new reality in research and in applying our insights to customer applications is not linear, but far more complex and dynamic. We need to keep that field open.

Prof. Dr. Michael Kaschke:

Absolutely, and that’s why I firmly believe that “rotating” people between science and industry wherever possible – for example through exchange and sabbatical programs – can benefit everyone. It is this change of perspectives that opens up new horizons. I think institutions like Fraunhofer are perfect for this. This is where basic and industrial research come together and can be integrated into applications.

With Chirped Pulse Amplification (CPA) a high energy can be focused on a small point of matter. Due to the extremely short duration of the pulse, only the matter directly targeted by the laser beam is vaporized. The neighbouring regions are not affected. Longer pulses would also broadly heat up the surrounding material. CPA thus has particular application advantages. In the medical field, the finest tissues can be modified with high precision – in operations on the eye, such as cataracts or ametropia, for example.

High power lasers have been continuously improved since the 1980s. In the Fraunhofer Cluster of Excellence Advanced Photon Sources (CAPS), twelve institutes are currently working on new technologies in the field of ultra-short pulse lasers (USP). Systems with more than 100 watts are already available. The Fraunhofer Institutes for Applied Optics and Precision Engineering IOF in Jena and for Laser Technology ILT in Aachen are testing USP lasers in the multi-kilowatt range. Applications are increasingly found in the industry. After glass cutting and applications in measuring and medical technology, advancements are made in the large-scale processing of surfaces.

Professor Mourou, did you ever think about creating your own company based on CPA?

Prof. Dr. Gérard Mourou:

No. These are two very different things. I enjoy research but I also know about the amount of work it takes to establish a company – especially in the medical field. I saw this for the company, IntraLase, which I was involved with.

Prof. Dr. Michael Kaschke:

Would you encourage your students to go down this route?

Prof. Dr. Gérard Mourou:

Yes, I probably would. But you have to be very careful because when you’re a student in a lab and you have all the equipment you need, it’s very easy and you think you’re in a perfect world. But in business and in product development, you have to take into account many requests from different players and sometimes even conflicts of interests. It’s a completely different situation.

Prof. Dr. Michael Kaschke:

I think institutions like Fraunhofer IOF or the new ZEISS Innovation Hub at KIT in Karlsruhe can play a vital role in bridging this gap in knowledge transfer, from fundamental science to industry.

Prof. Dr. Andreas Tünnermann:

Fraunhofer is a unique platform and a kind of institution that probably only exists in Germany and a few other countries in Europe. It is an accelerator that will ensure this interplay remains intact in the future. We can be very close to applied fundamental research, do fundamental research ourselves, but also have an understanding of how transfer it and have an established relationship with industry and industrial development.

Prof. Dr. Michael Kaschke:

That’s the nice thing about this interplay. One player pushes in one direction, the others follow for a while and then discover new things – and we all learn something.